Recovery of solvent in solvent treating processes



April 26, 1938.

G. A. BEISWENGER RECOVERY OF SOLVENT IN SOLVENT TREATING PRGCESSES Filed July 30, 1932 I 2 Sheets-Sheet 1 I I I v I INVENTOR.

- ATTORNEY.

April 26, 1938.- G. A.'BE\SWENGER 2,115,003

RECOVERY 0F SOLVENT IN SOLVENT TREATING PROCESSES 2 Sheets-Sheet 2 Filed July 30, 1932 an an, N

I BY

ATTORN Y.

Patented Apr. 26, 1938' UNITED. STATES nscovsar or SOLVENT m sonvanr mama raocsssas Gustav A. Beiswenger, Elizabeth, N. 1., auignor to Standard Oil Development Company, a corporation of Delaware Application July so, 1932, Serial No. 628,333'

14 Claims.

This invention relates to the treatment of hydrocarbon oils with a selective solvent and more specifically relates to the recovery of the solvent from the treated oil. The invention has particular reference to the treatment of heavy hydrocarbon oils with light hydrocarbons.

The term heavy hydrocarbon oil" will be understood to mean lubricating distillates, cylinder oils, topped crudes, crude bottoms and tarry 10 or asphaltic residues or sludges, whether obtained by the distillation, cracking or destructive hydrogenation of petroleum oils, shale oils, coals, tars, pitches, bitumens or other carbonaceous material, or whether prepared synthetically by l the polymerization'of hydrocarbons in the presence of agentssuch as aluminum chloride or by the condensation of aromatic and parafllnic hydrocarbons in the presence of condensing agents such as for example the condensation products so of halogenated paraflln wax and naphthalene.

The term light hydrocarbons will be understood to mean liquefied hydrocarbons or mixtures of liquefied hydrocarbons of one to five carbon atoms, such as for example, ethane, propane,

25 butane, pentane, or mixtures of these.

In the treatment of heavy hydrocarbon oils with light hydrocarbons it is necessary to remove the light hydrocarbon solvent fromfthe treated oil. This may be accomplished by simao pie distillation. I have found, however, that it may be more advantageously accomplished by heating the oil-solvent mixture to a temperature at which the oil becomes substantially in soluble in the solvent, and then separating the V35 oil and solvent layers.

My invention therefore comprises heating a mixture of hydrocarbon oil and light hydrocarbon solvent to a temperature close to the critical temperature of the light hydrocarbon, if the 40 solvent comprises a single light hydrocarbon,

or to a temperature between the critical temperatures of the two light hydrocarbon components if the solvent comprises two light hydrocarbons, whereby the oil becomes substantially 45 insoluble in the solvent and then separating the two layers. 1 I

Two important advantages of separating the solvent from the heavy hydrocarbon oil in this manner over separation by true distillation are 50 that distillation and condensation equipment may be largely dispensed with, and heat exchange and other operations are greatly simplified.

The method of carrying out the separation 55 will be fully understood from the following description read with reference to the accompanying drawings" which are semi-diagrammatic views in sectional elevation of suitable types of apparatus for my purposes and of which Figure 1 illustrates the simplest embodiment 5 of the invention in which the oil is treated with solvent in a single stage and the solvent is then recovered from the treated oil and returned to the treating step, and

Figure 2 illustrates another embodiment of the invention in which the solvent recovery method is applied to a process for deasphalting and dewaxing a heavy hydrocarbon oil in the presence of light hydrocarbons.

Referring to Figure 1, numeral I designates a lo supply tank for the oil to be treated and numeral 2 denotes a supply tank for the light hydrocarbon solvent which for convenience in description may be referred to as propane. Pump 3 drawsoil from tank I through line and forces it through line I into a mixing device 8 which may ,be of any suitable type. Pump I draws propane from tank 2 through line '8 and forces it through lines 0 and i also into mixing device 6, wherein the oil and solvent are thoroughly commingled. From mixer 8 the flux of oil and solvent flows through line l0 into a settling chamber ll wherein normally solid materials contained in the oil, such as asphaltic and resinous bodies, which are thrown out by the propane, are allowed to settle. 'Ihe sludge of asphaltic or resinous material containing some propane is drawn off from settler ll through line l2. The small amount of propane present in this sludge can be removed by distillation (equipment not shown). The remainder of the material in settler II which comprises the bulk of the oil and solvent is removed therefrom through line i3 by pump I4 and forced through-line it into and through a heat exchanger I 8 and thence 40 through line I! intoa heater l8 wherein the-oilsolvent mixture is heated to a temperature close to the critical temperature of the solvent. In this case, in which the solvent comprises propane, the mixture will be heated to a temperature between, say, 180 and 204 F. (the approxi-' mate critical temperature of propane) The hot flux then flows through line H! into a separating chamber 20 wherein the oil being substantially insoluble in the propane at this temperature settles to the bottom. The oil which contains some propane is withdrawn therefrom through line 2i and its propane content removed by distillation (equipment not shown). The propane is removed through line 22 and forced heat by pump a through one :4 into and through changer I I. It flows-thence through line int a cooler 26 from which it is returned by means of pump'll' through lines 21, 9 and I to. themixer 8 where it may be used to treat fresh through line 33 and forces it through line 34,'

into mixer 35. Pump 38 draws propane from .tank' 3| through line 31 and forces it through lines 38 and 34 also into mixer 35. The flux of oil and propane flows through line 39 into a settling chamber 40 wherein precipitated asphaltic material is allowed'to settle. This is removed through line H and its propane content removed by distillation (equipment not shown). The remaining solution in settler 40 is withdrawn therefrom throughline 42 by pump 43. Since the solvent concentration in this solution is considerably higher than that desirable for dewaxing, part of the solution is passed through line 45 into and through a heat exchanger 48, whence it leaves through line 41 and is passed intoa heater 48 wherein it is heated to a temperature between say 180 and 204 F. (the approximate critical temperature of propane). The heated material then flows through line 49 into a separating chamber 50 wherein the oil, which is substantially insoluble in the propane at this temperature, settles to the bottom. The upper layer, which comprises substantially oil-free propane, passes out through line 5| into and through heat exchanger 46, partially preheating the cold solution, thence through line 52, cooler 53 and line 54' into line 38 to be reused in the process. The oil layer is withdrawn from settler 50 through line 55 and passed through cooler 55. The cooled oil passes through line 51 and mixes with by-passed solution coming through line 58. By controlling the proportional quantitiesof solution passed through lines 45 and 58 the concentration of oil in the solution resulting from the mixing of the streams from lines 51 and 58 can be maintained at any value which is found to be desirable for the dewaxing step. Thus for example it is generally desirable to use about 10 volumes of solvent per volume of oil in the deasph'alting operation whereas about 4 volumes of solvent per volume of oil is a suitable proportion for dewaxing. The mixed solution passes through line 59 into and through a cold exchanger 60, whence it leaves through line GI and passes through a chilling means 82 wherein it is chilled to a temperature below the wax separation point of the oil. Chilling means 62 may be of any suitable type such as the double pipe type illustrated, and any suitable refrigerant may be used. The chilled flux thence flows through line 63 into a settler ill wherein the wax is allowed to settle out. The wax sludge is withdrawn through line- 65. The remaining dewaxed flux is withdrawn from settler 65 through line 86 by pump 61 and-forced through line 68 into and through the cold exchanger 60 wherein it serves partially to chill the entering wax-containing flux. From the cold exchanger 00 the partially warmed dewaxed solution flows through line 50 into and through a heat exchanger 10 and thence flows through line H into a heating means 12 wherein it is heated to a temperature between say 180 and 204 1''. (the approximate critical temperature of propane). The heated material then flows through line is into a separating chamber ll wherein the oil which is substantially insoluble in the propane at this temperature setties to the bottom. The oil layer which contains some propane is withdrawn through line II and its propane content may be removed by distillation (equipment not shown). The solvent which is substantially free from oil is removed through line 16 and passed into and through heat exchanger 10 wherein it serves partially to preheat cold dewaxed flux withdrawn from the chiller. From heat exchanger 10 the partially cooled recovered solvent flows through line 17 into cooler 18 and thence maybe returned by lines I9 and 38 to the mixer 35 where it may be used to treat fresh oil.

In carrying out my method of solvent recovery the treated flux of oil and solvent should in gen are! be heated to a temperature within 30 F. be-

low and 30 F. above the critical temperature of the solvent, preferably within 10 F. above or below the critical temperature. This is true, however, only if the solvent comprises a single light hydrocarbon. .If a mlxed'solvent compris ing two light hydrocarbons is used, the flux should be heated to a temperature between the respective critical temperatures of the two light hydrocarbons. I The exact temperature to which it must be heated will, of course, depend upon the particular light hydrocarbons used in the solvent and the proportions in which they are present therein.

The pressure maintained on the flux of oil and solvent while being heated 'to temperatures close to the critical should preferably be within 50 pounds per square inch above or below the vapor pressure of the pure solvent at the particular temperature to which the flux is heated.

When the flux is heated to below the critical temperature and maintained above the vapor pressure of the solvent, the solvent is substantially in the liquid state. When however the flux is maintained below the critical temperature and below the vapor pressure or the solvent, the solvent may be considered to be in the vapor state.

At temperature above the critical the solvent may be in the homogeneous phase, which is neither liquid nor vapor. I have found that when operating within 20 F. of the critical temperature and within 50 pounds per square inch of the vapor pressure of the solvent, the variation in physical charcteristics of the solventin either the liquid, vapor or homogeneous phase is so small that the process can be operated successfully wlthinthese limits regardless of the state in which the solvent may exist. I

This method 01 recovering a light hydrocarbon solvent from oil-light hydrocarbon mixtures is applicable to all types of processes in which a heavy hydrocarbon material is treat-.

ed with a light hydrocarbon solvent: It will be understood that various modifications of the method may be made to adapt it to use in any particular combination of treating steps.

This invention is not limited by any theory of I its mechanism nor by any details which have been given merely ior purpose of illustration, but is limited only in and by the following claims in which I wish to claim all invention. I

novelty inherent in the auspos critical temperature 'and pressure of the solvent, and separating the oil layer from the solvent layer.

2. Process according to claim 1 in which the oilsolventmixtureisheatedtoatemperature within about 30 F. below and 80 1". above the critical temperature of the'solvent.

3. Process according to claim 1 in which the oil solvent mixture is heated to a temperature within about 20 F. below and 20 F. above th critical temperature oi the solvent.

4. Process according to claim 1 in which'the oil.

solvent mixture is heated to a temperature within about 10 F. belowand 10 1''. above the criti-v cal temperature 01 the solvent.

5. Process according to claim 1 in which the oil solvent mixture is under a pressure within 50 pounds per square inch above and 50- pounds per square inch below the sure of the solvent.

6..Process according to claim 1 in which the oil solvent mixture is heated to a temperature within about 80 1''. below and 30 1''. above the critical temperature of the solvent under a pressure within 50 pounds per square inch above and 50 pounds per square inch below the critical prescritical pres- 'sure of the solvent.

7. Process according to claim 1 in which the oil solvent mixture is heated to a temperature within about 20 1''. below and 20 1". above the critical temperature or the solvent under a pressure within 50 pounds per square inch above and 50 pounds per square inch below the critical pressure oi the solvent. v

8. Process according to claim 1 in' which the oil solvent mixture is heated to a temperature within about 10 1'. below and 10 l","above the critical temperature or the'solvent under a pressure within 50 pounds per' square inch above and 50 pounds per square inch below the critical pressure oi the solvent.

0. Inaprocessi'ortreatingheavyhydrocarbon oil with liuuciled propane, the method oi. recovering the propane from the treated oil which comprises heating the propane-oil mixture to near the critical temperature of propane, whereby the oil and propane become substantially immiscible. in one another, and separating the oil layer from the propane layer.

10. In a process !or treating heavy hydrocarbon oil with a mixture of light hydrocarbons, the method of recovering the light hydrocarbons, from the treated oil which comprises heating-the oillight hydrocarbon mixture to a temperature between the critical temperatures of the several light hydrocarbons while maintaining a pressure suflicient to retain the light hydrocarbons in liquid phase, and separating the oil layer from the light hydrocarbon layer. w

11. Process ior treating heavy hydrocarbon oil which comprises diluting the oil with a light hydrocarbon whereby asphaltic bodies are caused to precipitate, removing the preclpitated asphaltic bodies, chilling the remaining solution to a temperature at which wax is caused to separate, removing the wax, heating the wax-tree solution to a temperature near thecritical temperature oi the light hydrocarbon, whereby the oil and light hydrocarbon become substantially immiscible in each other, and separating the oil layer from the light hydrocarbon layer.

l2.- Process according to claim 11 in which the light hydrocarbon comprises propane.

13. The method oiseparating a ligh hydrocarbon solvent from a mixture of the same with a heavy hydrocarbon oil, which comprises heating the oil-solvent mixture to a temperature at which the oil becomes substantially insoluble in the solvent and then separating the oil and solvent layers.

14. The method oi separating liquefied propane {mm a mixture of the same with a heavy hydrocarbon oil, which comprises heating the propane-oil mixture to a temperature between the approximate limits 180 F. and 204 F. to cause the mixture to separate into a propane layer and an oil layer and separating these two layers.

GPSTAV A. BEISWENGER. 

